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2.6 & 7.1 DNA & RNA Structure Notes

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Presentation on theme: "2.6 & 7.1 DNA & RNA Structure Notes"— Presentation transcript:

1 2.6 & 7.1 DNA & RNA Structure Notes
IB Biology HL 1 Mrs. Peters Spring 2015

2 DNA DNA: deoxyribonucleic acid
Molecular basis of inheritance, genetic material

3 DNA Structure discovered by James Watson and Francis Crick in April 1953 their model was based on Rosalind Franklin’s x-ray data and Edwin Chargaff’s nucleotide data

4 RNA RNA: ribonucleic acid DNA “photocopy”
leaves nucleus to make proteins

5 U1. Nucleic Acids Nucleic Acids: type of macromolecule made up of nucleotides (monomers) Two types: DNA: Deoxyribonucleic Acid RNA: Ribonucleic Acid

6 U1. Nucleotide Structure
Phosphate group Pentose Sugar DNA: deoxyribose RNA: ribose Nitrogen base DNA (A,C,G,T) RNA (A,C,G,U) Held together by covalent bonds

7 S1. Nucleotide Structure Diagrams
Draw and label a nucleotide (in class)

8 U2. DNA vs. RNA (In Class) Feature DNA RNA Strand Double helix
Single strand Pentose Sugar Deoxyribose Ribose Nitrogen Bases A, C, G, T A, C, G, U Location Nucleus only Nucleus and cytoplasm

9 U3. DNA Structure Nitrogen Bases Purines: adenine (A), guanine (G)
Two rings Pyrmidines: cytosine (C), thymine(T) One ring

10 U3. DNA Structure Complementary Base Pairing:
A and T bonded by two H bonds C and G bonded by three H bonds

11 U3. DNA Structure Two nucleotides are bonded together in the center by hydrogen bonds forming a double helix Sugar and phosphate are covalently bonded, forming the “backbone” of each strand

12 U3. DNA Structure Double helix is made of two separate strands which are antiparallel 5’- 3’ 3’-5’ (upside down) 5’ end: phosphate group (PO43-) 3’ end hydroxide group (–OH) attached to sugar

13 U3. DNA Structure Draw and label a diagram of the molecular structure of DNA

14 DNA Structure Describe what is meant by the statement: “The structure of DNA is described as a twisted ladder.”

15 7.1 U2. Nucleosomes Nucleosomes help to supercoil DNA
8 histone proteins (octomer) with DNA wrapped around twice H1(specific histone protein) attaches the DNA to the octomer Linker DNA- short segment of DNA connects one nucleosome to another

16 7.1 S1. Hershey and Chase 1950’s Alfred Hershey and Martha Chase studied viruses to determine if genetic material was protein or DNA DNA contains phosphorous, proteins contain sulfur Used radioactive isotopes of phosphorous-32 and sulfur-35 in T2 bacteriophages (virus) which were injected into E. coli (bacteria)

17 7.1 S1. Hershey and Chase Trial 1:
Injected bacteria with T2 viruses that contained sulfur-35 in protein coats (on the outside) and normal DNA Used blender the gently shake the virus off the bacteria Bacteria produced no radioactivity, virus had the radioactive isotopes still attached

18 7.1 S1. Hershey and Chase Trial 2:
Injected bacteria with T2 viruses that contained phosphorous-32 in DNA, normal protein coats Used blender to gently shake virus off bacteria Bacteria produced radioactive DNA

19 7.1 S1. Hershey and Chase Conclusion:
DNA is the genetic material because the virus DNA had radioactive phosphorous which became present in the bacteria’s DNA

20 7.1 S1. Hershey and Chase

21 7.1 A1: Franklin and Wilkins
Rosalind Franklin was a research associate in biophysics unit at King’s College in London. Became skilled in techniques of crystallography and X-ray diffraction while researching other carbon compounds. Created the sharpest X-ray diffraction images of DNA in existence Through rigorous analysis of the patterns, she calculated the dimensions of the DNA helix

22 7.1 A1: Franklin and Wilkins
Maurice Wilkins worked in the biophysics unit at King’s College also. He also used X-ray diffraction to look at DNA Shared Franklin’s diffraction pattern and calculations to Watson, without Franklin’s knowledge or permission, before she could publish her findings.

23 7.1 A1. Franklin and Wilkins Deductions made by Franklin:
Cross in the center indicated a helix shape Angle of the cross shape showed the pitch of the helix Distance between horizontal bars shows the turn (3.4 nm apart)

24 7.1 A1. Franklin and Wilkins Deductions made by Franklin:
Distance between middle of pattern and top shows repeating structure Distance is 0.34 nm between repeats

25 DNA Structure Review What are the components of DNA?
How is 6 ft of DNA stored in every cell?

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